1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mean temperature of winding when current falls

  1. May 1, 2016 #1
    1. The problem statement, all variables and given/known data
    upload_2016-5-1_12-0-27.png

    2. Relevant equations
    R2=R1(1+alpha(t2-t1))

    3. The attempt at a solution
    R1=250/5=50ohms
    R2=250/3.91=63.94ohms

    R2=R1(1+alpha15degrees(t2-t1))
    63.94=50(1+1/254.5(t2-15))
    t2=

    Now I found this online but the answers provided still don't match, 84.25 being the closest.

    upload_2016-5-1_12-12-12.png

    When I manipulate the equation I get a totally different answer:
    63.94=50(1+1/254.5(t2-15))
    63.94/50=(1+1/254.5(t2-15))
    1.2788/1+1/254.5=t2-15
    1.274=t2-15
    t2=1.274+15=16.274 degrees

    Please help me understand where I am going wrong.
     
  2. jcsd
  3. May 1, 2016 #2

    cnh1995

    User Avatar
    Homework Helper

    upload_2016-5-1_12-12-12-png.100061.png
    Is this from B.L. Theraja?
     
  4. May 1, 2016 #3
    Not sure I found it online
     
  5. May 1, 2016 #4

    cnh1995

    User Avatar
    Homework Helper

    It is from B.L. Theraja. The page looks familiar. The red line in the above post is your error.
     
  6. May 1, 2016 #5
    What have I done wrong though? Every way I enter it into my calculator yields an incorrect answer
     
  7. May 1, 2016 #6

    cnh1995

    User Avatar
    Homework Helper

    This step is wrong. Check the sequence of operations.
     
  8. May 1, 2016 #7
    Ah I got it :-) thank you
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Mean temperature of winding when current falls
  1. When will ball fall off? (Replies: 20)

  2. Temperature a current (Replies: 4)

Loading...